If you are interested in Nikon D800 NEF raw images taken at high ISO, you can find them here. The files can be opened and edited using Nikon Capture NX 2.3.
The noise level at ISO as high as 6400 is stunningly low. The noises are definitely there if you zoom in but for practical purposes, they are very good.
[update: February 11, 2012]: Check out ISO 6400 samples from Nikon D800.
Keywords: D800, D800E, NEF, Nikon, Nikon D800, Nikon D800E